Various types of industrial facilities have boilers or vessels which are relatively large. Workers may have to enter the interiors of such vessels to engage in construction, repair, inspection, or testing. Vessels in which such work may be performed are found in fossel-fueled electric generating power plants, refineries, pulp mills, and other industrial facilities.
The work performed inside such a vessel may require the use of various tools, machines, and construction materials which must be moved into, and among various locations within, the vessel. Frequently, scaffolding must also be built up in the interior of the vessel.
Many types of vessels have large access ports through which larger tools, instruments, and materials can be passed, and these ports are usually located relatively low in the vessel. Thus, objects brought into the vessel through such access ports must then be raised to the higher elevations within the vessel.
Although such vessels may have auxiliary ports in the upper elevations, these higher ports, which may be used for inspection or other purposes, are typically relatively small (e.g., as small as 3"by 5"). Thus, most larger pieces of apparatus and material cannot be passed through such small ports.
The raising of larger objects from the bottom of the vessel interior to the upper elevations where that object is used has conventionally been effected by manually lifting the object in a bucket-brigade fashion up a scaffolding on the interior of the vessel. This is obviously very labor-intensive, and can be dangerous with heavy objects. Further, the final, precise positioning of the object at the higher elevation is difficult to control manually if the object is relatively heavy.
Accordingly, it would be desirable to provide an apparatus and method for supplying objects to the upper elevations of a vessel interior. It would be beneficial if an apparatus could be provided for lifting such an object to the precise elevation where it is needed. In addition, it would be advantageous if the apparatus could be large enough, and have enough power, to lift relatively heavy objects. It would further be desirable if such an apparatus could be designed to function as described even though the apparatus may be too large or heavy to permit installation of the entire apparatus inside of the vessel. Finally, it would be beneficial if such an apparatus could be controlled by workers inside the vessel.